keith, i'm not sure of the similarities of tr3 and tr4 wiring, but on the
'4 the wipers, brake lights, turn signals, and a few other systems i'm
not remembering at the moment, are all on the green circuit off the bottom
of the fuse box. on my car the clip holding the fuse to the terminals
was loose, preventing a good connection. i intend to get a new fuse box,
but in the mean time i'm using an inline fuse holder connected to empty
terminal posts on either side of the green circuit.
the green circuit only gets power when the key is on, so you might also
check that the light green wire at the ignition switch is getting juice
when you turn the key.
i hope this is helpful.